1. Field of the Invention
The present invention relates to an apparatus and method for sealing between two or more surfaces. Specifically, the present invention relates to an expandable packer for sealing oil field wellbores.
2. Background of the Related Art
FIG. 1 is a schematic view of a typical oil field well 10. A wellbore 12 is drilled through the strata 16 and a casing 14 is inserted therein to maintain the integrity of the wellbore for subsequent production of hydrocarbons from beneath the surface of the well. Typically, a replaceable tubing string 18, comprising a plurality of tubes that are longitudinally connected together, is inserted into the casing 14 to a certain depth in the well, such that the lower end of the tubing string is proximate a production zone 20 containing hydrocarbons. Perforations 22 are formed in the casing at the depth of the formation to be produced to allow the hydrocarbons to enter the wellbore 12 through the casing 14. In many cases, it is desirable that the hydrocarbons flow to the surface through the tubing string 18 to avoid corrosion and flow damage to the casing 14. In those cases, a sealing assembly, such as a packer 23, may be run on the lower end of the tubing string 18. The packer 23 seals an annulus between the tubing outside diameter and the casing inside diameter, thereby diverting the hydrocarbons to flow through the tubing to the surface. In other examples, a packer seal is effected inside the tubing string 18 and can be referred to as a plug. Alternatively, the packer may seal an annulus between a smaller tubing string (not shown) outer diameter and the tubing string 18 inner diameter.
FIG. 2 is a schematic cross sectional view of one commercially available permanent type packer 23. The packer is shown in a disengaged state, i.e., xe2x80x9crunning positionxe2x80x9d, on the left side of the schematic view and in an engaged state, i.e., xe2x80x9cset positionxe2x80x9d, on the right side of the view. The packer 23 includes a packer body 24 having a ridge portion 25. A lock ring housing 26 is disposed in an upper portion of the packer 23. A lock ring 43 is disposed between the lock ring housing 26 and the ridge portion 25. The lock ring 43 includes mating ridges 27 adjacent the ridges on the ridge portion 25. At least one upper slip 28 and typically a plurality of slips are disposed below the lock ring housing 26 and include a serrated outer surface where the serrations are typically referred to as wickers 29. The upper slip 28 is disposed about the circumference of the packer 23 and are used to hold the packer in position when the wickers 29 grip the casing 14. An upper cone 30 is disposed below the upper slip 28. The upper cone 30 includes a tapered surface 41 that mates with a corresponding tapered surface on the upper slip 28. The upper cone 30 is used to displace the upper slip 28 radially outward as an axial force is applied to the slip 28 in a direction toward the upper cone. A pair of backup rings 31, 32 is disposed below the upper cone 30 and includes tapered surfaces that allow the backup rings to be displaced toward the casing 14 during xe2x80x9csettingxe2x80x9d of the packer into a sealing position. A seal ring 33 is disposed below the backup ring 32. A deformable packing element 34 is disposed below the seal ring 33 and is typically an elastomeric material that can be axially compressed and radially expanded toward the casing 14 to effect a seal. A corresponding arrangement of elements is disposed below the packing element 34 as is disposed above the packing element. The arrangement of members below the packing element includes a seal ring 35, a pair of backup rings 36, 37, a lower cone 38 having a tapered surface 42, and a lower slip 39 having wickers 40.
To set the packer 23, mechanical or hydraulic methods can be used and are well known in the art. Regardless of the method used to set the packer, generally the objective is to lower the packer attached to a tubing string to a setting depth and axially compress the assembly of external components relative to the packer body. The axial compression causes at least a portion of the external components, such as the slips 28, 39 and the packing element 34, to expand radially outward into engagement with the casing 14. The lock ring housing 26 and the lock ring 43 are forced along the ridge portion 25 of the packer body 24 as the slips and the packing element are radially expanded. When the desired amount of longitudinal compression is reached, the ridges on the ridge portion 25 in cooperation with the ridges 27 on the lock ring 43 maintain the lock ring and the lock ring housing 26 in the set position. The wickers 29, 40 of the slips 28, 39 xe2x80x9cbitexe2x80x9d into the casing surface to hold the packer 23 in position.
Elastomeric materials are frequently used for the packing element 34 and other sealing elements because of the resiliency of the elastomeric materials. However, under certain adverse conditions, elastomeric elements may be insufficient for the duty. Adverse conditions such as high temperatures, high pressures, and chemically hostile environments are common in downhole oil field wells that produce hydrocarbons. For example, the temperatures and/or pressures can cause extrusion of elastomeric elements and can result in leakage past the packer after installation. Another problem associated with elastomeric elements is xe2x80x9cswab offxe2x80x9d, where a pressure differential between two surfaces of the elastomeric element, such as the inner and outer surfaces, can deform the element and cause the element to become dislodged from the tool during run-in.
Providing a ductile metal as the packing element has been suggested as one solution to the failure of elastomeric elements. Thus, a xe2x80x9cmetal to metalxe2x80x9d contact is theoretically made between, for example, the packing element and the casing inside diameter that is less prone to extrusion under such adverse circumstances. However, typical manufacturing tolerances of the casing leading to nonconformities, such as the casing ovality, typically reduce the sealing capabilities of the metal to metal contact and leakage can result. Further, even if an initial seal occurs, the seal may leak under changing conditions of temperature and/or pressure, because the metal is not sufficiently resilient.
Prior efforts, such as shown in U.S. Pat. No. 2,519,116, incorporated herein by reference, to effect metal to metal contact have employed detonating explosive charges disposed on a rod within a packer cavity to expand an outer ductile metal wall of the packer. The expanded metal wall engages the casing and forms a metal to metal contact. However, once deformed from the explosion, the cavity is no longer able to expand to meet changing conditions.
Further, U.S. Pat. No. 2,306,160, also incorporated herein by reference, teaches a fluid injected into a cavity to inflate the cavity and effect a seal. The reference discloses that suitable liquid materials injected into the cavity are those liquids which harden after expansion and, thus, are unable to meet changing conditions.
Therefore, there remains a need for a metal sealing assembly with increased sealing capabilities and sufficient resiliency, particularly under adverse conditions in an oil field well.
The invention generally provides a sealing assembly with a deformable portion and a core at least partially disposed within the deformable portion that can be radially expanded to engage an adjacent surface and effect a seal. In one embodiment, the core is a fluid-containing core that preferably comprises a compressible fluid and the deformable portion comprises a deformable metal. The core can retain an amount of stored energy and adjust to changing conditions that otherwise might affect the seal integrity. The core can be sealed within the deformable portion and can be compressed by a force applied to the deformable portion to cause radial expansion. The core can also be coupled to a piston which can apply a force to fluid within the core to cause the radial expansion necessary to effect sealing. An elastomeric member can be attached to the deformable portion to assist in sealing.
In one aspect, the invention provides a sealing assembly comprising a deformable portion and a fluid-containing core that deforms the deformable portion toward a surface and retains a quantity of stored energy for further deformation. In another aspect, the invention provides a method of sealing between two surfaces comprising positioning a sealing assembly adjacent a surface, increasing a pressure of a fluid in a fluid-containing core in the sealing assembly, deforming a deformable portion of the sealing assembly toward the surface, engaging the surface, and retaining an amount of stored energy in the core after engaging the surface. In another aspect, the invention provides a packer for use in a wellbore comprising a deformable portion and a fluid-containing core within the deformable portion that radially expands the deformable portion in the wellbore. The core can retain stored energy after the radial expansion occurs. In another aspect, the invention provides a sealing assembly comprising a deformable portion and a core that expands the deformable portion toward a surface and retains a quantity of stored energy for further deformation. In another aspect, the invention provides a sealing assembly comprising a deformable portion, a fluid-containing core disposed at least partially within the deformable portion, and a piston in communication with the fluid-containing core.